You can solve for C using the law of cosines.
P, Q, and R are the angles of the triangle and p, q, and r are the lengths of the sides of the triangle opposite of the angles. That means p = 10ft, q = 12ft, and r=5ft. The law of cosines states that:
Since we're looking for the measure of angle P, we would use the first equation,
. Plug the values we have for the sides of the triangle into the equation and solve for P:
The measure of angle P is about 55<span>
°.</span>